This study will thoroughly investigate the potential role and significance of cartilage T2 relaxation time as a potential outcome marker for early osteoarthritis. It will focus on asymptomatic (according to WOMAC pain score) subjects of the incidence cohort of the OAI with varying degrees of physical activity, who are at increased risk for osteoarthritis. A number of these subjects will eventually develop osteoarthritis over the course of this 48 months longitudinal study and the proposed data analysis will provide unique information on the evolution of MR based biomarkers in this cohort. The specific aims are (I) to assess prevalence of cartilage, meniscal and ligamentous lesions in subjects from the incidence cohort of the OAI aged 45-60 years without pain using the whole organ magnetic resonance imaging score (WORI\/IS) in relation to physical activity determined by the physical activity scale for the elderly (RASE) and physical performance tests, (II) to measure cartilage T2 of all joint compartments combined and separately and correlate these quantitative measurements with prevalence and grade of focal cartilage, meniscal, ligamentous and bone marrow lesions as well as measurements of physical activity and physical performance, (IIIA) to analyze whether baseline T2 values will predict focal lesion progression diagnosed with H/OR/WS, clinical changes in KOOS (Knee Injury and Osteoarthritis Outcome Score) indices and eventually changes in PASE after 24 and 48 months and (IIIB) to longitudinally assess changes in T2 values, radiographic findings and focal joint lesions diagnosed with morphological MR sequences (WORMS) in relation to changes of pain scales, PASE and physical performance over a period of 48 months. The study will be performed in 300 subjects recruited from the incidence cohort of the OAI with no pain based on WOMAC scores, age 45-60 years and normal body mass index at baseline. Semiquantitative and quantitative MR imaging parameters will be analyzed in relation to clinical findings over a period of 4 years. We strongly believe, that the advances in knowledge that we gain through this study will help us better understand the role of T2 values in OA in relation to the evolution of OA and will help in focusing our preventive efforts on the earliest disease stages. This study may also provide evidence on life style factors that may be modified to prevent the development of osteoarthritis. RELEVANCE (See instructions): The combined analyses of morphological and quantitative MR imaging findings in relation to clinical findings will help us better understand the evolution of osteoarthritis at its earliest stages. Assessing cartilage matrix quality determined with T2 measurements may potentially gain a similar role in predicting risk of osteoarthritis such as bone mineral density currently has in predicting osteoporotic fractures. This longitudinal study performed in patients from the incidence cohort of the OAI will for the first time provide evidence whether cartilage T2 can predict development of OA, study MR findings associated with the evolution of OA and potentially give evidence on how long-term to prevent osteoarthritis and disability.